JPH04251427A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve a traveling property by providing a back coat layer contg. truly spherical nonmagnetic powder having the average grain size ranging from 0.1mum to 1.5mum and <=1.5 grain size distribution (D25/D75) in the rear surface of the magnetic recording medium. CONSTITUTION:This magnetic recording medium is provided with the back coat layer contg. the truly spherical nonmagnetic powder having the average grain size ranging from 0.1mum to 1.5mum and <=1.5 grain size distribution (D25/D75) in the rear surface of a base body having a magnetic layer on the front surface.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a magnetic recording medium such as a magnetic tape having a back coat layer on the back side of a substrate having a magnetic layer on the surface thereof, and more particularly to a magnetic recording medium such as a magnetic tape having excellent running properties. Regarding recording media.

0002

[Prior Art] In general, in magnetic recording media such as magnetic tapes, it is necessary to effectively prevent winding irregularities and scraping of the base film during high-speed winding to improve runnability and durability. Therefore, a back coat layer containing non-magnetic powder such as carbon black or alumina is provided on the back surface of a substrate having a magnetic layer. (Unexamined Japanese Patent Publication No. 51-306
No., Japanese Patent Publication No. 52-102004)

0003

[Problems to be Solved by the Invention] However, the non-magnetic powders such as carbon black and alumina conventionally used for the back coat layer have very fine particle sizes, so the surface roughness is smooth. If the shape is too angular and the improvement in running performance is not sufficient, or if the shape is angular or the axis ratio between the long axis and the short axis is different, it may be scraped while running and cause powder to fall off. However, the problem is that the running performance is not sufficiently improved.

0004

[Means for Solving the Problems] This invention has been made as a result of various studies in view of the current situation.
In the layer, the average particle diameter is within the range of 0.1 μm to 1.5 μm, and the particle size distribution (D25/D75) is 1.
By containing true spherical non-magnetic powder with a diameter of 5 or less, uniform microprotrusions are formed on the surface of the back coat layer, the coefficient of friction is sufficiently reduced, and running properties are sufficiently improved. .

In the present invention, the non-magnetic powder contained in the back coat layer has an average particle size of 0.1 μm to 1 μm.
．． Within the range of 5 μm, particle size distribution (D25/D75
) is preferably 1.5 or less, and if such a spherical nonmagnetic powder with an average particle size and uniform particle size distribution is included in the back coat layer, the surface roughness will be reduced. It does not become too smooth, and uniform microscopic protrusions are formed on the surface of the back coat layer, which effectively prevents air from being drawn in during running, and improves running performance without causing irregular winding. be done. In addition, by using true spherical non-magnetic powder with a uniform particle size distribution, there is no problem of powder falling off due to scraping during running, and the height of the protrusions can be controlled, so the backcoat layer can be The influence of unevenness on the magnetic layer can be sufficiently suppressed.

On the other hand, if particles with an average particle diameter of less than 0.1 μm are used, the surface roughness of the back coat layer becomes too smooth, the coefficient of friction increases, and running properties deteriorate. Furthermore, if a particle having a diameter larger than 1.5 μm is used, even if it is perfectly spherical, a large amount of non-magnetic powder will fall off, contaminating the running system, which is not preferable. In addition, particle size distribution (D2
5/D75) is larger than 1.5, scratches may occur even if the particle size has moderate runnability.
Running performance cannot be sufficiently improved.

Specific examples of such non-magnetic powders include:
For example, the average particle size is between 0.1μm and 1.5μm.
Spherical silica powder, polymethyl methacrylate powder, benzoguanamine powder, etc., which are within the range of μm and have a particle size distribution (D25/D75) of 1.5 or less, are preferably used. Powders are more preferably used. In addition, the amount used is preferably within the range of 3 to 20% by weight based on the total solid components contained in the back coat layer. Too little amount will cause uneven winding during running, and too much amount will cause surface roughness. This may cause them to drop out or drop out.

[0008] The formation of such a back coat layer is usually performed using true spherical particles with an average particle diameter in the range of 0.1 μm to 1.5 μm and a particle size distribution (D25/D75) of 1.5 or less. A back coat layer coating material is prepared by mixing and dispersing non-magnetic powder with a filler, a binder resin, an organic solvent, etc., and this is applied to the back surface of a substrate such as a polyester film on which a magnetic layer has been previously formed. , is done dry. The thickness of the back coat layer formed in this way is
It is preferably within the range of 0.1 to 2.0 μm,
More preferably, it is within the range of 0.3 to 1.2 μm.

[0009] Here, the binder resin used is as follows:
For example, cellulose resins, vinyl chloride-vinyl acetate copolymers, polyurethane resins, phenolic resins, amino resins, isocyanate compounds, radiation-sensitive resins, etc. are commonly used in magnetic recording media. Each of these can be used alone or in combination of two or more.

[0010] As the organic solvent, conventionally commonly used organic solvents such as methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, toluene, ethyl acetate, tetrahydrofuran, and dimethyl formamide can be used alone or in combination of two or more. Ru.

[0011] Note that this back coat layer contains a lubricant,
Commonly used additives such as dispersants and antistatic agents may be optionally added.

The magnetic layer formed on the surface of the substrate is made of γ-F
e2 O3 powder, Fe3 O4 powder, Co-containing γ-
Fe2 O3 powder, Co-containing Fe3 O4 powder, C
rO2 powder, barium ferrite powder, Fe powder, C
A magnetic paint is prepared by mixing and dispersing magnetic powder such as o powder, Fe-Ni powder, etc. with a binder resin and an organic solvent that are commonly used in the past, and this magnetic paint is applied to the surface of a substrate and dried. Co, Ni
, Fe, Co-Ni alloy, Co-Cr alloy, Co-P,
It can also be formed by depositing a ferromagnetic material such as Co--Ni--P on a substrate by means such as vacuum evaporation, ion plating, sputtering, or plating.

As the substrate, films made of synthetic resins such as polyester, polyamide, polyimide, polyamide cellulose derivatives, and non-magnetic metal films are preferably used.

[0014]

[Example] Next, an example of the present invention will be described. Example 1 α-Fe magnetic powder (average particle size 0.18 μm
) 100
Parts by weight Vinyl chloride-vinyl acetate-vinyl alcohol copolymer (Sekisui 11.2
Manufactured by Kagaku Kogyo Co., Ltd., S-LEC A) Polyurethane resin (manufactured by Dainippon Ink Chemical Co., Ltd., T-5250)
8.8 〃 Carbon black (average particle size 0.024 μm)
6.0 〃 α-Al2 O3
(Average particle size 0.25μm)
8.0 Myristic acid

3.0 n-butyl stearate

3.0 〃 Cyclohexanone
115.0 〃
toluene

115.0 After thoroughly kneading and dispersing this composition using a sand grinder mill, 5 parts by weight of a polyfunctional polyisocyanate compound (Coronate L, manufactured by Nippon Polyurethane Industries, Ltd.) was added to prepare a magnetic paint. did. This was applied onto a polyester film having a thickness of 13 μm to a dry thickness of 3.0 μm, dried, and then calendered to form a magnetic layer.

Next, on the back side of the polyester film on which the magnetic layer was formed, the following paint for back coat layer was applied and dried to form a back coat layer with a thickness of 0.8 μm, and the paint was spread to a predetermined width. I cut it up and made magnetic tape. Paint for back coat layer Carbon black (manufactured by Cabot; Mogul L, volatile content 33.0 parts by weight)
5.0%, oil absorption 60cc/100g) Car
Bon Black (manufactured by Columbia; Sebacarb MT-C
I 4.1 〃, volatile content 0, oil amount 41cc/100g) α-Fe2 O3

1.4
〃 CaCO3

16.5 Nitrocellulose (manufactured by Asahi Kasei Corporation, Nitrocellulose HIG 1)
18.0 Polyurethane resin (manufactured by Nippon Polyurethane Co., Ltd., N-2309) 20.
2 〃 Polyfunctional polyisocyanate compound (
Japan Polyurethane Industry 6.8 〃
manufactured by Coronate L) Silica powder (average particle size 1.0 μm, particle size distribution 1.2, true spherical) 15
cyclohexanone

300 Toluene

300 〃

0
Example 2 A back coat layer was prepared in the same manner as in Example 1, except that the amount of silica powder used in the composition of the paint for the back coat layer in Example 1 was changed from 15 parts by weight to 10 parts by weight. A magnetic tape was made.

Example 3 A back coat layer was prepared in the same manner as in Example 1 except that the amount of silica powder used was changed from 15 parts by weight to 5 parts by weight in the composition of the paint for the back coat layer in Example 1. was formed and a magnetic tape was made.

Comparative Example 1 A back coat layer was formed in the same manner as in Example 1 except that the silica powder was omitted from the composition of the paint for the back coat layer in Example 1, and a magnetic tape was produced.

Comparative Example 2 A back coat was prepared in the same manner as in Example 1, except that the amount of silica powder used in the composition of the paint for the back coat layer in Example 1 was changed from 15 parts by weight to 2.5 parts by weight. A magnetic tape was prepared by forming a magnetic tape.

Comparative Example 3 A back coat was prepared in the same manner as in Example 1, except that the amount of silica powder used in the composition of the paint for the back coat layer in Example 1 was changed from 15 parts by weight to 0.5 parts by weight. A magnetic tape was prepared by forming a magnetic tape.

[0021] The magnetic tape obtained in each example and comparative example
Regarding the drive, we conducted an actual machine running test at a running speed of 1.5 m/s.
The magnetic tape was tested at speeds of 2.7 m/sec and 2.7 m/sec to observe the presence or absence of winding disorder in the magnetic tape, and to examine the influence of the surface shape of the back coat layer on the magnetic layer. The effect of the surface shape of the back coat layer on the magnetic layer was determined by measuring the transition of irregularities on the surface of the magnetic layer due to the shape of the back coat layer. This measurement was performed using WYKO's TOPO-3D, which measured the surface roughness without contacting the stylus, the height of the convex part of the unevenness, the depth of the concave part, the distance from the convex part to the concave part, The surface roughness was measured by contacting with a stylus.

Table 1 below shows the results.

[0023]

Effects of the Invention As is clear from Table 1 above, the magnetic tapes obtained in Comparative Examples 1 to 3 show winding disorder, whereas the magnetic tapes obtained in Examples 1 to 3 The magnetic tapes had no winding disorder, and the magnetic tapes obtained in Examples 1 to 3 had
All of them have the same surface roughness as the magnetic tapes obtained in Comparative Examples 1 to 3, and have little effect on the magnetic layer of the back coat layer. Therefore, the average particle size is 0.1 μm or less.
Within the range of 1.5 μm, particle size distribution (D25/D7
The magnetic tape of the present invention, which has a back coat layer containing true spherical non-magnetic powder with 5) of 1.5 or less, has significantly improved runnability compared to conventional magnetic tapes. I understand that.

Claims (2)

[Claims] [Claim 1] On the back surface of a substrate having a magnetic layer on the surface,
It is characterized by providing a back coat layer containing true spherical non-magnetic powder with an average particle size within the range of 0.1 μm to 1.5 μm and a particle size distribution (D25/D75) of 1.5 or less. magnetic recording medium 2. The magnetic recording medium according to claim 1, wherein the spherical nonmagnetic powder is silica powder.